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I think my cat is losing weight — how do I check and when should I worry?

Confirm it with the scale, not your eyes: weigh at home and log it. A sudden loss of more than about 5% of body weight in a week — or a steady downward drift — warrants a vet visit, even if your cat seems fine.Fact

Cats hide illness, and weight change often moves before behavior does. This page helps you measure and decide when to escalate; it never diagnoses the cause.

Applies to: Owners who suspect weight loss (or gain). An observation-and-escalation page, not a diagnosis page.

Steps

Check it properlyFact
  • Use the same scale, surface, and time of day; weigh before feeding
  • For small changes, weigh yourself, then you-holding-the-cat, and subtract
  • Log immediately — memory is unreliable for ounces
  • A body-condition check (ribs, waist, belly) complements the number
The escalation lineFact
  • Sudden loss of MORE than ~5% of body weight in a week = call the vet
  • A slow, steady drift down over weeks counts too — track the trend
  • Weight loss WITH a normal or big appetite is still a vet visit, not reassurance
  • Very young kittens and seniors: treat any abnormal change as a prompt to call
Pair it with other signsProfessional guidance
  • Note appetite, thirst, litter output, and energy alongside weight
  • Bring the logged trend to your vet — it shortens the path to answers
  • Don't change the diet to 'fatten up' before a vet has looked — you may mask a problem

Normal vs keep-watching

Normal: A stable weight month to month for your adult cat; kittens gain, seniors are watched closely.

Keep watching: Weekly (kittens/seniors) or monthly (adults) weight, body condition, appetite, and litter output.

When to contact a vet. More than ~5% weight loss in a week, a steady downward trend, or weight loss with any other change is a veterinary visit — this page helps you measure and decide to go, never diagnoses why or says it's safe to wait.

What changes this answer

  • Life stage (kitten/senior = weigh weekly, escalate faster)
  • Appetite direction (loss WITH big appetite still = vet)
  • Recent diet change (rule in/out with the vet, don't self-adjust)

Common mistakes

  • Judging weight by eye instead of the scale
  • Waiting because the cat 'acts normal'
  • Changing food to compensate before a vet visit

Sources

Real questions cat owners ask

  • How much weight loss is concerning in a cat?
  • How do I weigh my cat at home?
  • My cat is losing weight but eating — why?
The weight timeline in This Week turns 'I think he's thinner' into a dated trend your vet can act on. Set up your Cat Passport.

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